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setreuid(2)
NAME
  setreuid - Sets real and effective user IDs

SYNOPSIS
  #include <unistd.h> setreuid(
	  uid_t ruid,
	  uid_t euid );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  setreuid:  XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  ruid	    Specifies the new real user ID.

  euid	    Specifies the new effective user ID.

DESCRIPTION
  The setreuid() function sets the real and effective user IDs of the current
  process to the values specified by the ruid and euid parameters.  If ruid
  or euid is -1, the corresponding effective or real user ID of the current
  process is not changed.

  Users may change the effective user ID to the real user ID; only processes
  with superuser privilege may make other changes.  This task is normally
  done by the system's authentication program (for example, login), but is
  not done for system daemons.

RETURN VALUES
  Upon successful completion, a value of 0 (zero) is returned.	Otherwise, a
  value of -1 is returned and errno is set to indicate the error.

ERRORS
  The setreuid() function sets errno to the specified values for the
  following conditions:

  [EINVAL]  The value of the ruid or euid parameter is invalid or out of
	    range.

  [EPERM]   The current process is not the superuser and a change other than
	    changing the effective user ID to the real user ID was specified.

RELATED INFORMATION
  Functions: getuid(2), setgid(2), setregid(2), setruid(3)

  Standards: standards(5)